1. Field of the Invention
The present invention relates to a display panel, and more particularly to a display panel cascade driver and capable of transmitting at least two different common voltages to a common electrode.
2. Description of the Related Art
With the advance in science and technology, display panel has become indispensable to modern people's everyday life. Examples of the application of display panel include TV, computer screen, personal digital assistant, and mobile phone. The popular application of display panel has brought great convenience and lots of fun in terms of entertainment and recreation.
The liquid crystal display panel includes a thin-film transistor substrate, a color filter substrate, a liquid crystal layer, a printed circuit board, and several flexible circuit films. The liquid crystal layer is disposed between the thin-film transistor substrate and the color filter substrate. The thin-film transistor substrate includes several pixels, each defined by any one scan line and any one data line interlaced with each other. The scan lines are corresponding electrically connected to several scan driving circuits, and the data lines are corresponding electrically connected to several data driving circuits, wherein the data driving circuits are electrically isolated from each other. Thus, the printed circuit board transmits a signal to a corresponding data driving circuit via every flexible circuit film. Generally, one flexible circuit film corresponds to one data driving circuit. The printed circuit board transmits a signal to a scan driving circuit via one flexible circuit film. Each pixel includes a thin-film transistor and a pixel electrode. The thin-film transistor has a gate, a drain and a source, wherein the gate, the drain and the source are electrically connected to a corresponding scan line, a pixel electrode and a data line, respectively. When the scan driving circuit provides a scan signal to turn on the gate of the pixel of each row sequentially, the data voltage transmitted via the data line will be inputted to the pixel electrode via the thin-film transistor whose pixel is turned on, so that the pixel electrode receives a pixel voltage.
The color filter substrate includes one color filter and one common electrode, wherein the color filter is covered by the common electrode. The peripheral of the common electrode is electrically connected to the circuit of the thin-film transistor substrate via silver pastes or gold ball. The printed circuit board transmits a set of fixed common voltage to the common electrode from the peripheral of the common electrode via the flexible circuit film, the circuit of thin-film transistor substrate and silver pastes or gold ball. The liquid crystal layer disposed between the common electrode and the pixel electrode can obtain a corresponding cross-voltage, that is, the voltage difference between the pixel voltage and the common voltage, from each pixel to rotate the liquid crystal molecules. Thus, when a light source is provided to the display panel, each pixel generates necessary change in luminance. Supposing the direction of the electric fields applied to the liquid crystal layer are the same, the arrangement of the liquid crystal molecules will deteriorate due to the long duration of the same rotating direction. To avoid the liquid crystal layer from generating the above rotation deterioration, a data voltage inverse driving method is provided. According to the data voltage inverse driving method, positive-polarity data voltage and negative-polarity data voltage are alternately provided to the same pixel as the pixel voltage of each pixel in different time intervals.
However, after the pixel electrode receives the pixel voltage, when the gate is turned off, a feed-through effect will occur due to the parasitic capacitance between the gate and the drain. As a result, when the gate is turned off, the pixel voltage will slightly drop off due to the feed-through effect. Therefore, the pixel voltage actually received by the pixel electrode is slightly less than the data voltage transmitted from the data line. Meanwhile, gate delay will occur due to the resistance of the scan line and the parasitic capacitance between the scan line and its neighboring conductor. That is, on the same scan line, the farther away from the scan driving circuit, the worse the gate delay will be. Thus, in the same row of pixels, the farther away from the scan driving circuit, the worse the distortion of the voltage wave of the pixel electrode will be due to the above gate delay. Furthermore, as the common electrode receives the common voltage by the edge of the common electrode, the resistance effect of the common electrode will cause the voltage at the central area of the common electrode to be less than the voltage at the edge area. Conventionally, the display panel only provides one common voltage to the common electrode. When the pixel is driven according to the data voltage inverse driving method, the above gate delay effect and the distortion of the voltage wave effect that the voltage at the central area of the common electrode being less than that at the edge area will cause the display panel to produce a image flicker phenomenon, and the larger the display panel is, the worse the image flickering will be. Conventionally, the display panel corresponds to one data driving circuit by one flexible circuit film, and this is very costly in the manufacturing process.